Working with polling firm Mustel Group, Vancity found that 94 per cent of respondents believed Black Friday prices were, on average, an estimated 23 per cent lower than they were at other times of the year.

One-third of those polled had bought something on Black Friday, while 76 per cent believed that retailers were making less money on the sales.

Vancity's research said otherwise. The credit union reported that large retailers "often work backwards with suppliers to set starting prices," which helps secure their profit margins in the event of price markdowns.

In fact, Vancity noted a Wall Street Journal article saying that from 2009 to 2012, the profit margins at major U.S. retailers remained about the same, with holiday sales making barely any difference.

The credit union also reported data from 360pi Corporation showing that prices "did not change significantly on Black Friday" in 2013, and that they actually went up in a number of cases.

Indeed, as the following graph shows, retailers including Target and Walmart actually raised their prices last year.

Meanwhile, research from Market Track LLC, a price-tracking company, found that the prices of 366 products climbed, on average, about eight per cent leading up to Thanksgiving, only to be dropped on Black Friday.

The prices of toys and tools had climbed the most in that period, by around 23 per cent each.

Vancity also scrutinized "door-crasher sales." The credit union cited research showing that stores were lowering prices on a "very small number of highly advertised items" while raising prices elsewhere, in an effort to draw shoppers to them first.

"It is well known that the first store a customer visits on Black Friday will secure the largest share of their wallet," the report said.

The credit union went on to note research showing that "92 per cent of 2013 Black Friday ads contained at least one item selling for the same price as the retailer had sold the item for on Black Friday in 2012."

It was a similar story from 2013 to 2014: an estimated 93 per cent of retailers "duplicated door-buster offers from one year to the next."

Vancity's advice to shoppers was to look up the best prices and products, shop around Black Friday, not just on the day, and to think carefully before going out and splurging.

The credit union isn't the only party offering financial advice ahead of Black Friday.

Last week, Blake Elyea, senior-vice president at accounting firm Grant Thornton, told The Huffington Post Canada that shoppers should be especially wary when buying products on their credit cards, because they can end up spending more than the purchase price.

"Don't get drawn into impulse purchases and sales and buying things you don't need," he said.